1. Field of the Invention
The present invention relates to a teleconference system that includes a wide variety of television monitors and video cameras.
2. Description of the Prior Art
Several teleconference systems have been proposed so far, such as that shown in Japanese Laid-Open Patent Publication No. 63-65789.
FIG. 1 schematically shows a previously proposed teleconference system in use. As shown in FIG. 1, this kind of teleconference system includes television monitors 18a, 38a which are respectively installed in first and second conference rooms 10, 30 to display situations of one conference room on the television monitor of the other conference room so that a conference can be held between the respective occupants of conference rooms 10, 30. Generally, data such as video data are transmitted between the two conference rooms 10, 30 via a telephone network line such as an integrated services digital network (ISDN) or the like. Therefore, the amount of data to be transmitted is limited by the telephone network line and an image such as an ordinary television broadcasting image having a high resolution cannot be transmitted in a real time fashion. It is therefore customary that the video image signal is transmitted in a compressed form.
Although an image displayed on the receiving side by the conventional teleconference system is deteriorated in resolution and cannot satisfactorily follow a moving image that is moving at high speed, this deterioration of resolution is not so important inasmuch as the teleconference system is utilized because only the state of one conference room is displayed on the television monitor of the other conference room.
When an electronic conference is held according to the conventional teleconference system, it is customary that not only the state of one conference room is displayed on the television monitor of the other conference room but also pictures of previously-prepared documents or the like are displayed on the television monitor of the other conference room. According to the conventional teleconference system, not only can the conference be conducted but also a variety of presentations can be made smoothly.
When various documents are displayed on the television monitor as described above, however, deterioration of resolution does become a problem. That is, when the document or the like is transmitted to and displayed on the television monitor in the other conference room, the deterioration of resolution becomes a serious problem because a displayed picture must have a resolution sufficient so that characters or the like written on the document can be visually confirmed. When a video signal reproduced from a video tape is transmitted to the receiving side, and if the video signal is compressed and then transmitted according to the conventional teleconference system, then the picture of the moving object is deteriorated considerably in resolution.
Further, such presentation involves a cumbersome operation. That is, various video information portions must be sequentially transmitted to the receiving side in accordance with the progress of the conference. Therefore, the conventional teleconference system needs an expert to operate the transmitting apparatus in addition to the conference attendees.